Food shortages, in other words, are not found only in the remote north and south of Ethiopia. They are inside the capital city itself, on the very doorstep of the military and self-proclaimed Marxist government of Mengistu Haile Mariam.

Prolonged drought has meant a shortage of teff nationwide. Yet the government is sensitive about letting the outside world see the lines here in Addis.

Recent requests by Western television crews to photograph them were refused. Officials said such pictures were ''not suitable.'' The government prefers to focus world attention on the urgent need for food aid outside the capital.

It is also reluctant to admit food shortages so soon after September's lavish celebrations of the 10th anniversary of Mengistu's seizure of power from the late Emperor Haile Selassie.

The celebrations saw Mengistu adopt Leninist terminology for his government (the Provisional Military Council, or Dergue, became the ''Politburo'') and Addis is still festooned with newly painted communist slogans such as ''Long live proletarian internationalism'' and pictures of Marx, Engels, and Lenin.

Just off Revolution Square in Addis stands Africa's largest statue of Lenin himself, not far from ragged bands of hungry farmers who straggle into the capital looking for food. Relief agencies report regular arrivals in Addis of these bands of refugees, whose fields have turned to dust after three or four years without rain. Zimbabwe lures tourists and foreign exchange

In Zimbabwe, it is not just food and water that is in short supply. Foreign exchange is scarce as well.

Robert Mugabe's government allocates hard currency sparingly. Its main money earners abroad are tobacco and other raw materials but it needs much more than it makes. Industry after industry reports difficulties in obtaining raw materials or consumer goods from abroad.

When I visited the Save the Children (US) offices in Harare, associate director Mofota Griffith-Shomari was scouring the city looking for a tire for the agency's four-wheel-drive vehicle. On the way back from an outlying area in eastern Zimbabwe, one tire had blown out. Because the tire had been retreaded once and could not be used again, the urgently needed vehicle was immobile.

The local Dunlop Tire Company says it lacks foreign exchange to buy carbon black, bead wire, stearic acid, sulfur and zinc oxide to make its tires and inner tubes.

Harare was heartened in November by the announcement that the United Kingdom had allocated 1 million Zimbabwe dollars (about $710,000) to import these raw materials. This brought to $1.26 million the aid the UK has provided since January for Dunlop Zimbabwe.

''But we shouldn't be dependent on foreign aid for money to make tires,'' said a local white businessman. ''The country ought to be earning more so that it can pay for its own tires. . . .''

One way the Mugabe government hopes to earn more foreign exchange is tourism. A new Zimbabwe Tourism Development Corporation aims to boost the annual flow of 350,000 tourists here to 1 million, partly by stronger advertising of the national airline, Air Zimbabwe. Zimbabwe develops sturdier strain of maize

Behind the scenes, research continues into one of Africa's greatest needs: new basic food crops that are resistant to drought and disease.

In the Arcturus district north of Harare, Rex Tattersfield and Bob Henson are testing 4,000 varieties of seed maize (corn) provided by the Zimbabwe government and 3,000 more developed on their Rattray Arnold Research Station.

''We have about 200 acres planted with the maize,'' Mr. Henson says, ''but it takes a long time to develop a good new strain: up to 14 years.

''The research station was started in 1974. We're hoping that the first hybrid maize seed developed here will be released to Zimbabwe farmers next season.''

Tested varieties of government seeds are exported to other African countries. The research station is testing other seeds as well: wheat, barley, sorghum, soybeans, peanuts (called groundnuts here), and sunflower. US comes up with new sorghum hybrid

Meanwhile, the US Agency for International Development (AID) reports in Washington that another promising step forward has been taken in African crop research.

Since 1970, the International Crop Research Institute for the Semi-Arid Tropics and Texas A&amp;M University have been involved in a project that has produced a commercial sorghum hybrid. Sorghum is a staple crop in Africa, but so far it has been low on research priorities. Now testing in central Sudan has indicated yields more than 50 percent higher than local varieties, AID reports.